ABT-737–induced apoptosis through the mitochondrial pathway. (A) KMS-12-PE cells were treated with 40nM ABT-737 for the indicated times. Cell death was analyzed by annexin-V staining. Cleavage of caspases-3 and -9 correlated with cell death. (B) Bax and Bak activation was determined by staining with antibodies against active forms in KMS-12-PE cells either treated or not with ABT-737. One representative experiment of 3 is shown. (C) LP-1 cells were transfected with the indicated siRNA for 72 hours before being treated with ABT-737 for 24 hours. Equivalent amounts of cell lysates were separated by SDS-PAGE and then immunoblotted with the indicated antibodies. Cell death was assessed by Apo 2.7 staining. Results represent the mean of 3 independent experiments. Statistical analysis were performed by paired Student t test: *P < .05; **P < .005.